Re: Why not just use KVM and oVirt?
Well, you are right, the hardware list is limited. That is largely irrelevant to smaller users, since it works, and works very well on hardware that is not on the list, and never was. There are many small/home labs running XenServer, since you got a lot of features for nothing.
The point is not to resurrect the API, but to provide a full-featured platform that does not have the newly imposed restrictions that have landed courtesy of Citrix. The platform was good before that, and hopefully this incarnation will be again.
If the coffee is CentOS, that would be why the starting point is CentOS.
One could equally ask "Why use KVM and oVirt?"